f The West Crocker Formation Outcrop at Kingfisher-Sulaman, Kota Kinabalu: Sedimentary Features and Facies Succession

A section of the West Crocker Formation (Oligocene-Lower Miocene) is spectacularly exposed at the Kingfisher-Sulaman residential district, along Jalan Sulaman, north of Kota Kinabalu in West Sabah. The ground clearing for the development project has exposed more than 200 m of deep-marine succession. This outcrop is one of many exposures that are the subject of an ongoing collaborative research by Petronas Research and Universiti Sains Malaysia. Some preliminary findings are presented in a separate presentation at this conference (Mohd Nizam et al., 2006). This poster is pictorial tour of the outcrop, arguably one of the best exposures of the West Crocker Formation. Over 230 m of steeply dipping, medium to thick-bedded sandstone and mudstone are exposed on the cut slopes of this outcrop. The sandstone facies is predominantly fine grained, though some are medium to coarse, and even pebbly (granular) in places. The beds range from a few 10s of metres to more than 30 m thick. Many have sharp tops and bases, the latter often erosive. Internally they appear to be structureless, though faint consolidation lamination or dish structures are quite common. Some beds have well-developed load and flame structures. Flute marks and rip-up clasts are also common, indicative of the erosive nature of the depositing flows. There are some thin turbidite units (< 1 m) with graded bedding and Bouma subdivisions, but these do not appear to be very common. A most spectacular feature of this outcrop is the occurrence of a slump interval at the top of the succession, consisting of several large (metre-scale) sandstone blocks “floating” in a muddy matrix. The succession may be subdivided into four main intervals, comprising coarsening-upward and fining-upward parasequences. The lowermost interval, comprising five fining-upward cycles, represents eposits of a channel complex. This is overlain by a sand-dominated interval interpreted to be middle to lower fan lobe complex. The third interval is a simple, fining-upward parasequence, which is thought to have been deposited within the upper fan/slope channel. The uppermost interval is mud-dominated and characterized by the presence of large sandstone blocks in shale, which is interpreted to represent muddy inter-channel/slope deposit. Most of the sandstone units in the Kingfisher-Sulaman outcrop were probably deposited as highdensity flows (debrites) rather than turbidites. The sandy nature of the succession and the preponderance of debrites and slump features suggest that the succession represents part of mass-transport complex in a slope or base-of-slope setting.